This invention is related to a motor vehicle occupant protection system, and in particular, to an air cushion restraint system design for providing crash protection for the vehicle driver.
Air cushion restraint systems (ACRS) are in widespread use in modern motor vehicles These systems comprise a fabric air bag which is folded and mounted to the steering wheel hub or to some other part of the instrument panel of the vehicle. In the event of a serious vehicle impact, deceleration sensors cause an inflator to generate a non-combustible inflation gas which fills the air bag and causes it to be deployed. Upon inflation, the folded air bag is ejected from the steering wheel or instrument panel in front of the vehicle occupant and acts as a restraint for absorbing impact energy acting on the occupant, thus restraining the occupant from high acceleration contact with surfaces of the vehicle interior compartment.
Conventional ACRS use an inflator having a propellant which generates all of the inflation gas for deploying the air bag. The inflator and its propellant charge must be adequate to ensure generation of a sufficient volume of gas to fully inflate the air bag. More recent ACRS designs incorporate an aspiration feature in which ambient air is allowed to enter the air bag during inflation to supplement the gas volume generated by the inflator. This principle operates since, upon inflation, a high velocity jet of gas escapes from the inflator. This jet of gas forces the air bag to inflate explosively which generates localized low pressure areas within the air bag. By providing flow paths exposing these low pressure areas to ambient air, the total gas volume of the deployed air bag can be comprised of the combination of gases generated by the inflator and aspirated ambient air. Such aspirated systems have a number of advantages. By mixing ambient air with the hot gases generated by the inflator, the average temperature of the gases within the air bag is reduced. This temperature reduction is important since, upon deflation of the air bag, hot exhausted gases pose the hazard of injuring the vehicle occupant. Moreover, since a reduced quantity of propellant is needed, the inflator itself can also be reduced in size, providing advantages of packaging, cost, and weight.
Although aspirated ACRS designs are presently known, they typically require a specific inflator unit design in order to operate effectively. Moreover, such systems are not readily adapted for various applications in which the air bag internal volume is varied or the frontal crash characteristics or "pulse" of the vehicle require different inflation rates or pressures. In addition, typical aspirated ACRS designs require a number of specific hardware components which require special packaging, and can be bulky and expensive to produce.
The ACRS of the present invention is particularly adapted for use for the driver's position of a motor vehicle and is intended to be mounted to the vehicle steering column. The ACRS of this invention uses available off-the-self inflators which are mounted to a special base plate which together provide for aspiration enhanced inflation while minimizing special parts and packaging problems In fact, the structure is sufficiently compact and efficient to enable packaging in existing steering wheel ACRS environments virtually without rework. The ACRS of this invention is easily adapted or "tuned" for differing applications since the position and total area of the aspiration air inlets can be easily modified without reworking the inflator.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.